The present invention relates to apparatus for grading agricultural, horticultural and other articles and particularly to improved grading rolls therefor.
Apparatus is known from applicant's prior disclosure, No. EP-A-0285226, wherein the articles, such as tulip bulbs, onions and the like are passed over a pair of parallel counter rotating rolls. Each roll is generally cylindrical and is provided on its periphery with a number of annular grooves, which are uniformly spaced in the axial direction along the length of the roll. Each roll is further provided with a flat or chordal portion extending longitudinally along its length so that the flat portion is closer to the central axis of the roll than the remaining surface of the cylinder. Additionally, guide strips, extending from the upper end of the flat portion downwards through the dimension of one or more of the axially spaced grooves, are provided.
The grading rolls are rotated counter to each other, with the flat portions arranged in opposition to each other such that the circumferential surfaces at the top of the rolls move away from each other, and the grooves form holes between the rolls. Thus articles, when placed on the rolls, are graded by the fact that correspondingly-sized articles fall through the holes formed between the grooves, while articles larger than the holes are carried forwardly along the axis of the cylinder by the guides. When the large articles reach the axial end of the grading rolls, they are transferred by the guiding strips onto a similar formed and arranged pair of grading rolls with larger holes.
It has appeared, in practice, that the known apparatus presents some danger in that articles may become trapped and thereby damaged, e.g. cracked, between the flattened surfaces of the rolls. This may happen, particularly if there are inaccuracies in the rotational velocity of the rolls, which has to be adapted to the slant angle of the guiding strips provided on the flat surfaces. Furthermore, the provision of the guiding strips on the rolls requires separate manufacturing of said strips and additional work in assembling the strips to the rolls.
It is an object of the present invention to provide grading rolls which are simpler and less expensive to construct.
It is a further objection of the present invention to provide grading rolls which are gentler and less damaging to the articles being graded.
Further objects and advantages of the present invention will be apparent from the following disclosure of the invention.